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Young blood reverses heart decline in old mice

By Douglas Heaven

Could a protein that’s more common in the blood of younger mice help revive ageing hearts?

(Image: Thomas J. Abercrombie/National Geographic/Getty)

Out with the old, in with the new. Pumping young blood around old bodies – at least in mice – can reverse cardiac hypertrophy – the thickening and swelling of the heart muscle that comes with age and is a major cause of heart failure.

Amy Wagers at Harvard University and Richard Lee at Brigham and Women’s Hospital in Boston, Massachusetts, and their colleagues wanted to see if a similar procedure might benefit the heart. The researchers surgically joined the circulatory systems of pairs of mice&colon; one a healthy two-month-old animal, the other a 23-month-old mouse that had cardiac hypertrophy. This enabled blood from each mouse to flow around the other.

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After just four weeks, the older mouse’s heart had reverted to almost the same size as that of its younger counterpart. “The hearts had shrunk as far as they were going to go,” says Wagers. “It was quite striking how the heart responded… they were pretty much the same as in the young partner.” The hearts of the young mice were unaffected, even though they were pumping some blood from the older mice.

Something in the blood

Since all parts of the body appear to age at the same rate, it makes sense that there should be something in the blood that coordinates ageing, says Wagers. “The bloodstream is a logical conduit for the body to use,” she says.

After ruling out the effect of reduced blood pressure on the older mice, the team identified a potential candidate&colon; a protein called GDF11, which was present in much higher quantities in the blood of the young mice.

To test the effect of GDF11, the researchers gave old mice with cardiac hypertrophy daily injections of it for 30 days. At the end of the treatment, their hearts were significantly smaller than those in a second group of mice of the same age and with the same condition, but that had been injected with saline. Heart cells shrank significantly in the first group of mice, the researchers found.

GDF11 is known to play an important role in cell development and healing, but no one had previously found a specific role for it within the heart. Wagers suggests it could be worthwhile to give low levels of GDF11 to people with cardiac hypertrophy. “We would hope that would result in similar effects.”

“This study emphasises once more the amazing plasticity of aged tissues and the apparent possibility to rejuvenate them,” says Tony Wyss-Coray at Stanford University in California, who was a member of the team that demonstrated the ability of the blood of young mice to reverse cognitive decline in elderly mice.

Saul Villeda at the University of California in San Francisco, who worked with Wyss-Coray on the cognitive decline study, suggests that young blood may contain other substances that rejuvenate other organs. He also notes that ageing involves many factors. “Counteracting ageing may prove to be a combination of inhibiting ageing factors and increasing youthful factors,” he says.